The economic impact of infectious diseases in food animal production is well documented. Infectious diseases reduce profits, increase production costs, and endanger food products, as well as affect the performance, health, and welfare of the animal. Diseases can reduce the yield and quality of milk resulting in great economic loss to dairy farmers and beef producers, particularly when in some cases infectious microbial diseases cause morbidity and mortality of newborn, young (e.g., replacement stock) or adult animals. Two such diseases, mastitis and bovine respiratory disease (BRD), can have devastating effects on food animal production.
Mastitis is defined as an inflammation of the mammary gland. It may affect any mammal, for example cows, ewes, and goats. Bovine mastitis is an infection of the udder of ruminants such as cows, mainly caused by gram positive and gram negative bacteria and especially in cows in intensive milk producing units. The bacterial infection results in the inflammation of the mammary gland (i.e. teats and udder). Animals may become more susceptible to mastitis due to impaired neutrophil microbicidal function during the periparturient period. The disease is particularly troublesome and of considerable economic importance because the pathogen is readily transferred from one animal to another during the milking process. It often develops in the first few weeks around parturition and can recur with each lactation. Some of the main pathogenic microorganisms causing bovine mastitis are Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis, Streptococcus dysgalactiae, Escherichia coli, Aerobacter aerogenes, Klebsiella pneumoniae, and Pseudomonas aeruginosa. See also Bovine Mastitis, edited by Glenys Bloomfield, V&O Publications 1987, hereby incorporated by reference. These microorganisms invade the udder through the teat canal and produce inflammation of the milk-producing tissue causing the formation of scar tissue which, once formed, may cause a permanent reduction in the cow's milk production. An infection can also alter the composition, quantity, appearance and quality of the milk. Mastitis-causing pathogens fall into two categories, namely, contagious and environmental. Contagious bacteria, such as streptococcus agalactiae and staphylococcus aureus, primarily colonize host tissue sites such as mammary glands, teat canals, and teat skin lesions; and are spread from one infected cow to another during the milking process. Environmental bacteria, often streptococci, enterococci, and coliform organisms, are commonly present within the cow's surroundings from sources such as cow feces, soil, plant material, bedding, or water; and infect by casual opportunistic contact with an animal. The distinction between contagious and environmental pathogens, although not exclusive, is of practical importance because different dairy herd maintenance measures are needed for the different groups of microorganisms. In all bovine mastitis cases, whatever the causal microorganism, the route of transmission of the invading pathogen into the inner gland of the udder is through the teat orifice and teat canal. The common sources of harmful microorganisms include unsanitary milking equipment, the milker, other mastitic animals, an unsanitary stable environment, and the animals' own elimination (defecation/urination) processes.
There are a variety of forms or types of bovine mastitis, with varying severity and symptomatology, including the following: (1) Udder infection: The invasion of the udder cavity by microorganisms that multiply within the gland and cause inflammation; (2) Nonclinical or subclinical mastitis; A form of mastitis in which there is no swelling of the gland or observable abnormality of the milk, although there are changes in the milk that can be detected by specific tests. This type of mastitis is by far the most prevalent and causes the greatest overall loss in most herds. It often is referred to as “hidden” mastitis: (3) Clinical mastitis; A form of mastitis in which the abnormal conditions of the udder and secretion are observable. Mild clinical mastitis involves changes in the milk such as flakes, clots, and a watery or unusual appearance. Heat and sensitiveness of the udder are slight or absent, but there may be signs of swelling. Severe clinical mastitis involves a sudden onset with swelling of the infected quarter which is hot, hard and sensitive. The milk appears abnormal and milk production drops. Sometimes, in addition to the local effects in the udder, the cow herself becomes sick. There are signs of fever, rapid pulse, depression, weakness and loss of appetite. The combination of these conditions often is referred to as acute systemic mastitis, because not only the udder, but the whole animal is affected; and (4) Chronic mastitis; A form of mastitis caused by a persistent udder infection that exists most of the time in the nonclinical form but occasionally can develop into an active clinical form. After these “flare-ups” the nonclinical form usually returns temporarily. (See generally Current Concepts of Bovine Mastitis, published by The National Mastitis Council, Inc., 2nd Ed. 1978 at p. 5.)
Mastitis continues to cause large economic losses to the dairy industry. Mastitis affects the profitability of a herd in a number of ways, both directly and indirectly, including: (1) loss of milk production; (2) higher culling rates of infected cows; (3) decreased value of milk; (4) discarded milk following antibiotic treatment; (5) veterinary costs (antibiotics and veterinary visits); and (6) deaths. (Bovine Mastitis, Glenys Bloomfield, supra, at p. 33.)
Another common disease affecting the cattle industry is shipping fever (bovine respiratory disease or BRD). BRD has been referred to by some as a “disease complex” for two reasons: it usually is caused by a variety of pathogens, both viral and bacterial, that interact with one another to produce full-blown disease, and because the behavior of the pathogens can follow a sequential process that, step by step, results in sick animals. Bacterial pathogens are one of the best known causes of the acute syndrome. The bacterial pathogens may invade the bovine respiratory tract after it has been compromised by a viral infection and other factors, such as the stress of weaning, shipping, change of feed and variation in ambient temperature and humidity, may precede and contribute to infection. In many instances this is added to the cattle's exposure to pathogens during shipping when they are commingling with cattle of other origin in trucks, stockyards and auction barns, resulting in the high incidence of the disease in cattle delivered to the feedlot.
Several species of bacteria have been isolated and associated with BRD, and some of the most common are Mannhemia haemolytica, Pasteurella mitltocida and (or) Histophilus somni. Haemophilus somnus is a virulent pathogen that causes septicemia in cattle and sometimes the resulting manifestations have been referred to as “Haemophilus somnus complex,” of which one form is respiratory disease, viruses such as infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD) and bovine respiratory syncytial virus (BRSV) may also be involved in initiating a BRD complex, often opening the door to secondary bacterial infections.
Because it is virtually impossible to eliminate these organisms from the environment, the BRD complex must be approached from the standpoint of preventing these disease-causing agents from taking hold, and detecting and treating clinical cases as quickly and effectively as possible. Respiratory diseases are a major cause of disease loss in beef cattle. It is generally recognized that the ultimate cause of death in most cases of shipping fever is a bacterial (usually pasteurella) pneumonia. Pasteurella haemolytica, particularly type 1A, is the most common bacterium isolated from cases of respiratory disease in North America. Vaccination against some of the infectious agents involved in shipping fever is sometimes helpful, but vaccines are available and efficacious for only a few of the agents known to be involved in the disease complex.
Antibiotic therapy has been a major component of mastitis and BRD control strategy. U.S. Pat. No. 7,182,948, which is incorporated by reference herein in its entirety, indicates that antimicrobial teat dips containing iodine have been shown to be effective against mammary infections and mastitis-causing bacteria (Pankey, J. W. et al., (1983) J. Dairy Sci. 66 (1), 161 167). These compositions are usually administered to the teat by dipping or spraying the teat prior to milking as well as after removal of the milking cup. To reduce mastitis, commercial teat dips have been developed containing a variety of antimicrobial agents including iodophors, quaternary ammonium compounds, chlorine release compounds (e.g. alkali hypochlorites), oxidizing compounds (e.g. hydrogen peroxide, peracids), protonated carboxylic acids (e.g. heptanoic, octanoic, nonanoic, decanoic, undecanoic acids), acid anionics (e.g. alkylaryl sulfonic acids), chlorine dioxide (from chlorite), and bisbiguanides such as chlorhexidine. These agents, which have varying degrees of effectiveness, limit the transmission of mastitis by reducing pathogen populations on the teat. However, there are problems associated with the use of antimicrobials. The most prevalent are irritation to the teat and teat cracking. To alleviate these problems, emollient additives such as glycerin and lanolin have been included in such compositions. However, even with the use of these emollients skin irritation can still occur.
U.S. Pat. No. 6,790,867, which is incorporated by reference herein in its entirety, indicates that subcutaneous injections of formulations combining a non-steroidal anti-inflammatory drug (NSAID) such as flunixin, with a fluorinated chloramphenicol or thiamphenicol derivative antibiotic such as florfenicol, may be used to treat BRD. U.S. Patent Application Publication No. 20070155799, which is incorporated by reference herein in its entirety, discloses new fenicol compounds that may be used as antibiotic prodrugs and in combination with NSAIDs or other antibiotics.
The NMC (formerly the National Mastitis Council), a not-for-profit organization devoted to reducing mastitis and enhancing milk quality, stresses the importance of proper teat sanitation, but also proper teat care for the prevention of mastitis. The economic harm caused by mastitis has led to much research in its control. Physical stresses as well as environmental conditions have been reported to be large contributors to mastitis infection. See U.S. Patent Publication No: 20020051789, which is incorporated by reference. Since it was documented that sub-clinical mastitis was directly related to poor teat condition (Neijenhuis, P. et al., (2001) J. Dairy Sci. (84) 2664 2672), a number of commercial teat dip solutions incorporating conditioning agents have evolved (National Mastitis Council, Summary of Peer-Reviewed Publications on Efficacy of Premilking and Postmilking Teat Disinfectants Published Since 1980; January 2002). Teat end callosity and roughness have been shown to have a direct relationship with clinical mastitis (Neijenhuis, F. et al., (2001) J. Dairy Sci. (84) 2664 2672). The reduction of chapping and irritation of teats as well as keeping the teat flexible is very important in controlling mammary infections. Glycerin has also been used as a teat conditioner in teat dip solutions. However, studies indicate no significant decrease in mastitis-causing bacteria such as staphylococcus aureus, streptococcus agalactiae, or coliforms when the glycerin content is increased from 2% to 10% in a 1% iodine teat dip solution (National Mastitis Council, Summary of Peer-Reviewed Publications on Efficacy of Premilking and Postmilking Teat Disinfectants Published Since 1980; January 2002). Thus, although products such as teat dip solutions are available, there is still an unmet need to modulate the incidence, recurrence, and/or severity of mastitis.
U.S. Pat. No. 5,849,883, which is incorporated by reference herein in its entirety, discloses a number of the antibiotics used in the treatment of mastitis including but not limited to, beta-lactam antibiotics such as penicillins (ampicillin, cloxacillin, hetacillin, nafcillin, penicillin G, (benzyl penicillin), procaine penicillin) and cephalosporins (cefoperazone, cefuroxime, Cefalonium, cefapirin, cefoxazole, cefracetrile); aminoglycoside antibiotics (framycetin, neomycin, novobiocin, streptomycin); macrolide antibiotics (erythromycin); tetracyclines (chlortetracycline, oxytetracycline); and polypeptide antibiotics (Polymyxin B). Antibiotic treatment for mastitis is usually given by means of intramammary infusions, either in lactating cows when clinical mastitis is detected, or at drying off (dry cow therapy). (Bovine Mastitis, supra, at p. 69.) In cases where severe clinical disease is present, antibiotics must be given parenterally since intramammary infusions are ineffective because of blockage of the ducts).
The early hopes that antibiotics would allow complete control of the disease have not been realized. None of the above mentioned antibiotics utilized thus far has been entirely satisfactory. Additionally, it has been found to be very desirable to replace antibiotic treatment with treatment by non-antibiotic chemo-therapeutic drug compounds, for the following reasons: (1) Antibiotics effective in human medicine should not be utilized in veterinary medicine, in order not to build up strain resistance of bacteria appearing in human diseases; (2) Antibiotics should be reserved for such diseases for which no chemo-therapeutic drug compound would be available, as it has been proved that bacterial strains build up resistance to an antibiotic after extended use of such antibiotic; and (3) Staphylococcus aureus, one of the above-noted pathogens, has already built up a resistance against most of the antibiotics utilized in the treatment of bovine mastitis.
One such method for treatment by a non-antibiotic chemo-therapeutic drug compound is described in U.S. Pat. No. 4,610,993, which is incorporated by reference herein, which claims a method for treating animals for bovine mastitis with an effective amount of at least one pyridine-N-oxide disulfide compound. Another method by the same inventors is described in U.S. Pat. No. 4,401,666, which is incorporated by reference herein, which claims a method for treating animals for bovine mastitis with an effective amount of at least one metallic salt of pyridine 2-thione-N-oxide. Despite these several published methods, it remains very important to find cost-effective methods utilizing non-antibiotic compounds which would substantially overcome the drawbacks of antibiotics used thus far and yet would be effective in treating and preventing mastitis.
Another common disease affecting the cattle industry is shipping fever (bovine respiratory disease). Respiratory diseases are a major cause of disease loss in beef cattle. The term “shipping fever” is used to describe the respiratory disease complex observed in cattle 6 months of age or older after shipment either into feedlots or onto pasture. The stresses of weaning, castration, dehorning, fasting, overcrowding, exposure to infectious agents, dietary changes, transportation, environmental temperature extremes, and other stressors combined with viral, bacterial, mycoplasmal, and/or chlamydial infections contribute to the shipping fever complex. Mixing calves from different farms and/or salebarns greatly facilitates exposure to infectious agents. U.S. Pat. No. 6,497,869, which is incorporated by reference herein, describes some of initial infectious agents that may affect cattle. Population mixing may be a more important predisposing factor to shipping fever than stressors, although disease can occur without mixing and stressors usually dramatically worsen respiratory disease. Attempts to reduce stress by weaning, castrating, dehorning, etc. and acclimating cattle to new diets days or weeks prior to shipment are sometimes successful (but may not be cost-effective) in reducing the incidence of shipping fever. Vaccination against some of the infectious agents involved in shipping fever is sometimes helpful, but vaccines are available and efficacious for only a few of the agents known to be involved in the disease complex.
It is generally recognized that the ultimate cause of death in most cases of shipping fever is a bacterial (usually Pasteurella) pneumonia. Pasteurella haemolytica, particularly type 1A, is the most common bacterium isolated from cases of respiratory disease in North America. Attempts to experimentally reproduce bacterial pneumonia in cattle are usually unsuccessful without severe stress and predisposing damage to the respiratory tract. It is generally believed that during times of stress, viruses, mycoplasma, and/or chlamydia most often provide the initial damage to the respiratory tract which predisposes to severe bacterial infection and disease.
A typical clinical respiratory disease outbreak usually begins within hours or days of the cattle's arrival at the feedlot. Recently shipped cattle in the 400 to 500 pound weight range commonly have 10 to 80% morbidity and 1 to 10% mortality, or more, to respiratory tract disease. When the serum of cattle is analyzed for a four-fold antibody rise (seroconversion) and the respiratory tract and its secretions subjected to microbiologic isolations, a myriad of etiologic agents can be identified. Many animals, those sick and those apparently healthy, can be shown to have undergone infection by one or more agents (respiratory tract disease is probably seldom due to only one infectious agent). Although bovine respiratory disease complex is recognized clinically in the feedlot after arrival, the infections giving rise to clinical disease probably start at the salebarns, where cattle are first assembled from different farms. See also Bovine Respiratory Disease, Loan, R. W. Texas A & M University Press, 1984, hereby incorporated by reference.
Administration of a compound that treats or modulates the incidence, recurrence, duration, and/or severity of mastitis or respiratory disease in cattle or other infections in non-human animals, including but not limited to, cattle, poultry, swine, horses, dogs, and cats would be useful in veterinary medicine. Examples of such infections include but are not limited to, neonatal septicemia in horses, pleuropneumaonia in pigs, and pneumonia in non-human animals. Such compounds may restore or modulate neutrophil function in the animal.
The growth hormone (GH) supergene family (Bazan, F. Immunology Today 11: 350-354 (1991); Mott, H. R. and Campbell, I. D. Current Opinion in Structural Biology 5: 114-121 (1995); Silvennoinen, O. and Ihle, J. N. (1996) SIGNALING BY THE HEMATOPOIETIC CYTOKINE RECEPTORS) represents a set of proteins with similar structural characteristics. Each member of this family of proteins comprises a four helical bundle. While there are still more members of the family yet to be identified, some members of the family include the following: growth hormone, prolactin, placental lactogen, erythropoietin (EPO), thrombopoietin (TPO), interleukin-2 (IL-2), IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-11, IL-12 (p35 subunit), IL-13, IL-15, oncostatin M, ciliary neurotrophic factor, leukemia inhibitory factor, alpha interferon, beta interferon, gamma interferon, omega interferon, tau interferon, epsilon interferon, granulocyte-colony stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GM-CSF), macrophage colony stimulating factor (M-CSF) and cardiotrophin-1 (CT-1) (“the GH supergene family”). Members of the GH supergene family have similar secondary and tertiary structures, despite the fact that they generally have limited amino acid or DNA sequence identity. The shared structural features allow new members of the gene family to be readily identified. Four helical bundle polypeptides are described in WO 2005/074650 entitled “Modified Human Four Helical Bundle Polypeptides and Their Uses,” which is incorporated by reference in its entirety.
A member of the GH supergene family is Granulocyte Colony Stimulating Factor (G-CSF). Granulocyte colony stimulating factor (G-CSF) is one of several glycoprotein growth factors known as colony stimulating factors (CSFs) because they support the proliferation of hemopoietic progenitor cells. G-CSF stimulates the proliferation of specific bone marrow precursor cells and their differentiation into granulocytes. It is distinguished from other CSFs by its ability to both stimulate neutrophilic granulocyte colony formation in semi-solid agar and to induce terminal differentiation of murine myelomonocytic leukemic cells in vitro. Granulocyte Colony-Stimulating Factor is a potent stimulus for neutrophil proliferation and maturation in vivo (Cohen et al., Proc. Natl. Acad. Sci. 1987; 84: 2484-2488 see also Heidari et al., Vet. Immunol. Immunopathol. 2001; 81:45-57, herein incorporated by reference). G-CSF is also capable of inducing functional activation or “priming” or mature neutrophils in vitro (Weisbart, R. H., Gasson, C. G., and D. W. Golde. Annals of Internal Medicine 1989; 110:297-303). G-CSF has been shown to prime human granulocytes, and enhance superoxide release stimulated by the chemotactic peptide, N-formyl-methionyl-leucyl-phenalalanine (S. Kitagawa, et al., Biochem. Biophys. Res. Commun. 1987; 144:1143-1146, and C. F. Nathan, Blood 1989; 74:301-306), and activate human neutrophil IgA mediated phagocytosis (Weisbart, R. H., et al., Nature 1988; 332: 647-649).
Neutrophils are a critical component of host defense mechanisms against bacterial and fungal infections. G-CSF is capable of inducing an increase in the absolute number of circulating neutrophils and enhances neutrophil function.
The cDNA cloning and expression of recombinant human G-CSF (hG-CSF) has been described, and it has been confirmed that the recombinant hG-CSF exhibits most, if not all, of the biological properties of the native molecule (Souza, L. et al. Science 232, 61-65 (1986)). Sequence analysis of the cDNA and genomic DNA clones has allowed the deduction of the amino acid sequence and reveals that the protein is 204 amino acids long with a signal sequence of 30 amino acids. The mature protein is 174 amino acids long and possesses no potential N-linked glycosylation sites but several possible sites for O-linked glycosylation.
The cloning and expression of cDNA encoding human G-CSF has been described by two groups (Nagata, S. et. al., Nature 319, 415-418 (1986); Souza, L. M. et al., Science 232, 61-65 (1986)). The first report of a G-CSF cDNA clone suggested that the mature protein was 177 amino acids in length. The authors reported that they had also identified a cDNA clone for G-CSF that coded for a protein that lacked a stretch of three amino acids. This shorter from of G-CSF cDNA expresses the expected G-CSF activity. The second report describes a cDNA sequence identical to this short form and makes no mention of other variants. Since these authors confirmed that the short cDNA expresses G-CSF with the expected profile of biological activity, it is probable that this is the important form of G-CSF and that the longer form is either a minor splicing variant or the result of a cloning artifact.
Matsumoto et al., in Infection and Immunity, Vol. 55, No. 11, p. 2715 (1987) discuss the protective effect of human G-CSF on microbial infection in neutropenic mice.
The following patent publications relate to G-CSF: WO 8703689, which is incorporated by reference herein, describes hybridomas producing monoclonal antibodies specific for human G-CSF and their use in the purification of G-CSF; WO 8702060, which is incorporated by reference herein, discloses human G-CSF like polypeptides and methods of producing them; U.S. Pat. No. 4,810,643, which is incorporated by reference herein, discloses human G-CSF like polypeptides, sequences encoding them and methods of their production; and WO 8604605 and WO 8604506, which are incorporated by reference herein, disclose a gene encoding human G-CSF and infection inhibitors containing human G-CSF. Isolation of h-GCSF and production of G-CSF in host cells such as E. coli are described in, e.g., U.S. Pat. Nos. 4,810,643; 4,999,291; 5,580,755; and 6,716,606, which are incorporated by reference herein.
G-CSF is a pharmaceutically active protein which regulates proliferation, differentiation, and functional activation of neutrophilic granulocytes (Metcalf, Blood 67:257 (1986); Yan, et al. Blood 84(3): 795-799 (1994); Bensinger, et al. Blood 81(11): 3158-3163 (1993); Roberts, et al., Expt'l Hematology 22: 1156-1163 (1994); Neben, et al. Blood 81(7): 1960-1967 (1993); Welte et al. PNAS-USA 82: 1526-1530 (1985); Souza et al. Science 232: 61-65 (1986) and Gabrilove, J. Seminars in Hematology 26:2 1-14 (1989)). G-CSF was purified to homogeneity from cell culture supernatants of the human bladder carcinoma cell line 5637 (Welte et al., Proc. Natl. Acad. Sci. (1985) 82:1526-30). The sequence of the cDNA coding for native hG-CSF is known from Souza et al., Science (1986) 232:61-65. As a consequence of alternative splicing in the second intron two naturally occurring forms of hG-CSF exist with 204 or 207 amino acids of which the first 30 represent a signal peptide (Lymphokines, IRL Press, Oxford, Washington D.C., Editors D. Male and C. Rickwood). The mature protein was shown to have a molecular weight of about 19 kDa and has 5 cysteine residues which can form intermolecular or intramolecular disulfide bridges. Binding studies have shown that bG-CSF binds to neutrophilic granulocytes. Little to no binding is observed with erythroid, lymphoid eosinophilic cell lines as well as with macrophages.
In humans, endogenous G-CSF is detectable in blood plasma (Jones et al. Bailliere's Clinical Hematology 2:1 83-111 (1989)). hG-CSF is produced by fibroblasts, macrophages, T cells, trophoblasts, endothelial cells and epithelial cells and is the expression product of a single copy gene comprised of four exons and five introns located on chromosome seventeen. Transcription of this locus produces a mRNA species which is differentially processed, resulting in two forms of hG-CSF mRNA, one version coding for a protein of 177 amino acids, the other coding for a protein of 174 amino acids (Nagata et al. EMBO J. 5: 575-581 (1986)), and the form comprised of 174 amino acids has been found to have the greatest specific in vivo biological activity. hG-CSF is species cross-reactive, such that when human G-CSF is administered to another mammal such as a mouse, canine or monkey, sustained neutrophil leukocytosis is elicited (Moore et al. PNAS-USA 84: 7134-7138 (1987)).
G-CSF can be obtained and purified from a number of sources. Natural human G-CSF (nhG-CSF) can be isolated from the supernatants of cultured human tumor cell lines. The development of recombinant DNA technology, see, for instance, U.S. Pat. No. 4,810,643 (Souza) incorporated herein by reference, has enabled the production of commercial scale quantities of G-CSF in glycosylated form as a product of eukaryotic host cell expression, and of G-CSF in non-glycosylated form as a product of prokaryotic host cell expression.
G-CSF has been found to be useful in the treatment of indications where an increase in neutrophils will provide benefits. G-CSF can mobilize stem and precursor cells from bone marrow and is used to treat patients whose granulocytes have been depleted by chemotherapy, or as a prelude to bone marrow transplants. For example, for cancer patients, G-CSF is beneficial as a means of selectively stimulating neutrophil production to compensate for hematopoietic deficits resulting from chemotherapy or radiation therapy. Other indications include treatment of various infectious diseases and related conditions, such as sepsis, which is typically caused by a metabolite of bacteria. G-CSF is also useful alone, or in combination with other compounds, such as other cytokines, for growth or expansion of cells in culture, for example, for bone marrow transplants.
The G-CSF receptor (G-CSFR) is a member of the hematopoietic/cytokine/growth factor receptor family, which includes several other growth factor receptors, such as the interleukin (IL)-3, -4 and -6 receptors, the granulocyte macrophage colony-stimulating factor (GM-CSF) receptor, the erythropoictin (EPO) receptor, as well as the prolactin and growth hormone receptors. See, Bazan, Proc. Natl. Acad. Sci. USA 87: 6934-6938 (1990). Members of the cytokine receptor family contain four conserved cysteine residues and a tryptophan-serine-X-tryptophan-serine motif positioned just outside the transmembrane region. The conserved sequences are thought to be involved in protein-protein interactions. See, e.g., Chiba et al., Biochim. Biophys. Res. Comm. 184: 485-490 (1992). The G-CSF receptor consists of a single peptide chain with a molecular weight of about 150 kD (Nicola, Immunol. Today 8 (1987), 134).
Glycosylated hG-CSF has been compared with de-glycosylated hG-CSF, prepared by in vitro enzymatic digestion with neuraminidase and endo-α-N-acetylgalactosaminidase, with respect to its stability as a function of pH and temperature (Oh-eda et al., 1990, J. Biol. Chem. 265 (20): 11432-35). The de-glycosylated hG-CSF, dissolved at a concentration of 1 μg/mL in 20 mM phosphate buffer containing 0.2 M NaCl and 0.01% Tween 20 was rapidly inactivated within the pH range of from about pH 7 to about pH 8 after a two-day incubation at 37° C. In contrast, glycosylated hG-CSF retained over 80% of its activity under the same conditions. Furthermore, evaluation of the thermal stability of both forms of hG-CSF, measured by biological assay and calorimetric analysis, indicated that de-glycosylated hG-CSF was less thermally stable than the native form of hG-CSF.
A number of approaches have been taken in order to provide stable, pharmaceutically acceptable G-CSF compositions. One approach to improving the composition stability of G-CSF involves the synthesis of derivatives of the protein. U.S. Pat. No. 5,665,863 discloses the formation of recombinant chimeric proteins comprising G-CSF coupled with albumin, which have new pharmacokinetic properties. U.S. Pat. Nos. 5,824,784 and 5,320,840, disclose the chemical attachment of water-soluble polymers to proteins to improve stability and provide protection against proteolytic degradation, and more specifically, N-terminally modified G-CSF molecules carrying chemically attached polymers, including polyethylene glycol.
Structures of a number of cytokines, including G-CSF (Zink et al., FEBS Lett. 314:435 (1992); Zink et al., Biochemistry 33:8453 (1994); Hill et al., Proc. Natl. Acad. Sci. USA 90:5167 (1993)), GM-CSF (Diederichs, K., et al. Science 154: 1779-1782 (1991); Walter et al., J. Mol. Biol. 224:1075-1085 (1992)), IL-2 (Bazan, J. F. Science 257: 410-411 (1992); McKay, D. B. Science 257: 412 (1992)), IL-4 (Redfield et al., Biochemistry 30: 11029-11035 (1991); Powers et al., Science 256:1673-1677 (1992)), and IL-5 (Milburn et al., Nature 363: 172-176 (1993)) have been determined by X-ray diffraction and NMR studies and show striking conservation with the GH structure, despite a lack of significant primary sequence homology.
An alternative approach to increasing stability of G-CSF in composition involves alteration of the amino acid sequence of the protein. U.S. Pat. No. 5,416,195 discloses genetically engineered analogues of G-CSF having improved composition stability, wherein the cysteine residue normally found at position 17 of the mature polypeptide chain, the aspartic acid residue found at position 27, and at least one of the tandem proline residues found at positions 65 and 66, are all replaced with a serine residue. U.S. Pat. No. 5,773,581 discloses the genetically engineered G-CSF analogues of G-CSF that have been covalently conjugated to a water soluble polymer.
The various forms of human G-CSF, including their preparation and purification, useful in a method for treating or preventing mastitis are described in detail in U.S. Pat. No. 4,810,643, which is hereby incorporated by reference. U.S. Pat. No. 4,810,643 describes and claims novel gene segments, biologically functional recombinant plasmids and viral DNA vectors and prokaryotic and eukaryotic host cells, which contain a G-CSF gene or a genetically engineered variant of a G-CSF gene. The host cells express biologically active G-CSF or a genetically engineered variant of G-CSF. U.S. Pat. No. 5,849,883 and WO 89/10932 describe various studies with human G-CSF in cattle, The studies were performed evaluated respiratory diseases (Pasteurella hemolytica), responses to bacterial challenges (Klebsiella pneumonia), or coliform mastitis (E. coli) in cattle.
U.S. Pat. No. 5,849,883, which is incorporated by reference herein in its entirety, presents the polynucleotide and polypeptide sequence of mature bovine G-CSF (bG-CSF), and describes methods to clone, isolate, and purify the polypeptide and analogs thereof. Mature b-GCSF is 174 amino acids in length (SEQ ID NO: 1) that has 82% homology to hG-CSF. A bG-CSF polypeptide with an initial methionine amino acid residue is shown as SEQ ID NO: 2. The polynucleotide sequence that encodes SEQ ID NO: 1 is shown as SEQ ID NO: 3. The polynucleotide sequence that encodes SEQ ID NO: 2 is shown as SEQ ID NO: 4. Heidari et al. describe the expression, purification, and biological activities of bG-CSF in Veterinary Immunology and Immunopathology (2001) 81:45-57.
Covalent attachment of the hydrophilic polymer poly(ethylene glycol), abbreviated PEG, is a method of increasing water solubility, bioavailability, increasing serum half-life, increasing therapeutic half-life, modulating immunogenicity, modulating biological activity, or extending the circulation time of many biologically active molecules, including proteins, peptides, and particularly hydrophobic molecules. PEG has been used extensively in pharmaceuticals, on artificial implants, and in other applications where biocompatibility, lack of toxicity, and lack of immunogenicity are of importance. In order to maximize the desired properties of PEG, the total molecular weight and hydration state of the PEG polymer or polymers attached to the biologically active molecule must be sufficiently high to impart the advantageous characteristics typically associated with PEG polymer attachment, such as increased water solubility and circulating half life, while not adversely impacting the bioactivity of the parent molecule.
PEG derivatives are frequently linked to biologically active molecules through reactive chemical functionalities, such as lysine, cysteine and histidine residues, the N-terminus and carbohydrate moieties. Proteins and other molecules often have a limited number of reactive sites available for polymer attachment. Often, the sites most suitable for modification via polymer attachment play a significant role in receptor binding, and are necessary for retention of the biological activity of the molecule. As a result, indiscriminate attachment of polymer chains to such reactive sites on a biologically active molecule often leads to a significant reduction or even total loss of biological activity of the polymer-modified molecule. R. Clark et al., (1996), J. Biol. Chem., 271:21969-21977. To form conjugates having sufficient polymer molecular weight for imparting the desired advantages to a target molecule, prior art approaches have typically involved random attachment of numerous polymer arms to the molecule, thereby increasing the risk of a reduction or even total loss in bioactivity of the parent molecule.
Reactive sites that form the loci for attachment of PEG derivatives to proteins are dictated by the protein's structure. Proteins, including enzymes, are composed of various sequences of alpha-amino acids, which have the general structure H2N—CHR—COOH. The alpha amino moiety (H2N—) of one amino acid joins to the carboxyl moiety (—COOH) of an adjacent amino acid to form amide linkages, which can be represented as —(NH—CHR—CO)n—, where the subscript “n” can equal hundreds or thousands. The fragment represented by R can contain reactive sites for protein biological activity and for attachment of PEG derivatives.
For example, in the case of the amino acid lysine, there exists an —NH2 moiety in the epsilon position as well as in the alpha position. The epsilon —NH2 is free for reaction under conditions of basic pH. Much of the art in the field of protein derivatization with PEG has been directed to developing PEG derivatives for attachment to the epsilon —NH2 moiety of lysine residues present in proteins. “Polyethylene Glycol and Derivatives for Advanced PEGylation”, Nektar Molecular Engineering Catalog, 2003, pp. 1-17. These PEG derivatives all have the common limitation, however, that they cannot be installed selectively among the often numerous lysine residues present on the surfaces of proteins. This can be a significant limitation in instances where a lysine residue is important to protein activity, existing in an enzyme active site for example, or in cases where a lysine residue plays a role in mediating the interaction of the protein with other biological molecules, as in the case of receptor binding sites.
A second and equally important complication of existing methods for protein PEGylation is that the PEG derivatives can undergo undesired side reactions with residues other than those desired. Histidine contains a reactive imino moiety, represented structurally as —N(H)—, but many chemically reactive species that react with epsilon —NH2 can also react eith —N(H)—. Similarly, the side chain of the amino acid cysteine bears a free sulfhydryl group, represented structurally as —SH. In some instances, the PEG derivatives directed at the epsilon —NH2 group of lysine also react with cysteine, histidine or other residues. This can create complex, heterogeneous mixtures of PEG-derivatized bioactive molecules and risks destroying the activity of the bioactive molecule being targeted. It would be desirable to develop PEG derivatives that permit a chemical functional group to be introduced at a single site within the protein that would then enable the selective coupling of one or more PEG polymers to the bioactive molecule at specific sites on the protein surface that are both well-defined and predictable.
In addition to lysine residues, considerable effort in the art has been directed toward the development of activated PEG reagents that target other amino acid side chains, including cysteine, histidine and the N-terminus. See, e.g., U.S. Pat. No. 6,610,281 which is incorporated by reference herein, and “Polyethylene Glycol and Derivatives for Advanced PEGylation”, Nektar Molecular Engineering Catalog, 2003, pp. 1-17. A cysteine residue can be introduced site-selectively into the structure of proteins using site-directed mutagenesis and other techniques known in the art, and the resulting free sulfhydryl moiety can be reacted with PEG derivatives that bear thiol-reactive functional groups. This approach is complicated, however, in that the introduction of a free sulfhydryl group can complicate the expression, folding and stability of the resulting protein. Thus, it would be desirable to have a means to introduce a chemical functional group into bioactive molecules that enables the selective coupling of one or more PEG polymers to the protein while simultaneously being compatible with (i.e., not engaging in undesired side reactions with) sulfhydryls and other chemical functional groups typically found in proteins.
As can be seen from a sampling of the art, many of these derivatives that have been developed for attachment to the side chains of proteins, in particular, the —NH2 moiety on the lysine amino acid side chain and the —SH moiety on the cysteine side chain, have proven problematic in their synthesis and use. Some form unstable linkages with the protein that are subject to hydrolysis and therefore decompose, degrade, or are otherwise unstable in aqueous environments, such as in the bloodstream. Some form more stable linkages, but are subject to hydrolysis before the linkage is formed, which means that the reactive group on the PEG derivative may be inactivated before the protein can be attached. Some are somewhat toxic and are therefore less suitable for use in vivo. Some are too slow to react to be practically useful. Some result in a loss of protein activity by attaching to sites responsible for the protein's activity. Some are not specific in the sites to which they will attach, which can also result in a loss of desirable activity and in a lack of reproducibility of results. In order to overcome the challenges associated with modifying proteins with poly(ethylene glycol) moieties, PEG derivatives have been developed that are more stable (e.g., U.S. Pat. No. 6,602,498, which is incorporated by reference herein) or that react selectively with thiol moieties on molecules and surfaces (e.g., U.S. Pat. No. 6,610,281, which is incorporated by reference herein). There is clearly a need in the art for PEG derivatives that are chemically inert in physiological environments until called upon to react selectively to form stable chemical bonds.
The use of conjugates of hydroxyalkylstarch, and in particular the use of hydroxyethylstarch (HES), covalently linked to a polypeptide have been disclosed in order to potentially alter the polypeptide's immunogenicity and/or allergenicity. HESylation is an alternative technology that has been disclosed in a series of patent applications assigned to Fresenius Kabi A B including U.S. Patent Publication Numbers 20050063943, 20060121073, 20010100163, 20050234230, 20050238723, 20060019877, 20070134197, 20070087961, as well as U.S. Pat. No. 7,285,661, all of which are incorporated herein by reference. TIES is a modified natural polymer that has been clinically used as a plasma volume expander and HESylation represents the technology of coupling drug substances with HES derivatives in order to modify drug characteristics, such as pharmacokinetics or water solubility. This also includes the prolongation of protein plasma circulation via an increased stability of the molecule and a reduced renal clearance, resulting in an increased biological activity. In addition, the immunogenicity or allergenicity might be reduced. By varying different parameters, such as the molecular weight of HES, a wide range of HES conjugates can be customized. Nevertheless, hydroxyethyl starch shares a common disadvantage with all other presently available polymers: its polydispersity. The polymer conjugates are a mixture of molecules having molecular weights distributed around an average value. This lack of homogeneity results in a low level of chemical and biochemical characterization and could prevent the pharmaceutically active component to reach its site of action (receptor, enzyme, etc.). In these cases the drug to be active requires its delivery in the original unconjugated form, and thus cleavage of the polymer by metabolic reactions is required for its pharmaceutical efficacy.
Recently, an entirely new technology in the protein sciences has been reported, which promises to overcome many of the limitations associated with site-specific modifications of proteins. Specifically, new components have been added to the protein biosynthetic machinery of the prokaryote Escherichia coli (E. coli) (e.g., L. Wang, et al., (2001), Science 292:498-500) and the eukaryote Sacchromyces cerevisiae (S. cerevisiae) (e.g., J. Chin et al., Science 301:964-7 (2003)), which has enabled the incorporation of non-genetically encoded amino acids to proteins in vivo. A number of new amino acids with novel chemical, physical or biological properties, including photoaffinity labels and photoisomerizable amino acids, photocrosslinking amino acids (see, e.g., Chin, J. W., et al. (2002) Proc. Natl. Acad. Sci. U.S. A. 99:11020-11024; and, Chin, J. W., et al., (2002) J. Am. Chem. Soc. 124:9026-9027), keto amino acids, heavy atom containing amino acids, and glycosylated amino acids have been incorporated efficiently and with high fidelity into proteins in E. coli and in yeast in response to the amber codon, TAG, using this methodology. See, e.g., J. W. Chin et al., (2002), Journal of the American Chemical Society 124:9026-9027; J. W. Chin, & P. G. Schultz, (2002), ChemBioChem 3(11):1135-1137; J. W. Chin, et al., (2002), PNAS United States of America 99:11020-11024; and, L. Wang, & P. G. Schultz, (2002), Chem. Comm., 1:1-11. All references are incorporated by reference in their entirety. These studies have demonstrated that it is possible to selectively and routinely introduce chemical functional groups, such as ketone groups, alkyne groups and azide moieties, that are not found in proteins, that are chemically inert to all of the functional groups found in the 20 common, genetically-encoded amino acids and that may be used to react efficiently and selectively to form stable covalent linkages.
The ability to incorporate non-genetically encoded amino acids into proteins permits the introduction of chemical functional groups that could provide valuable alternatives to the naturally-occurring functional groups, such as the epsilon —NH2 of lysine, the sulfhydryl —SH of cysteine, the imino group of histidine, etc. Certain chemical functional groups are known to be inert to the functional groups found in the 20 common, genetically-encoded amino acids but react cleanly and efficiently to form stable linkages. Azide and acetylene groups, for example, are known in the art to undergo a Huisgen [3+2] cycloaddition reaction in aqueous conditions in the presence of a catalytic amount of copper. See, e.g., Tornoe, et al., (2002) J. Org. Chem. 67:3057-3064; and, Rostovtsev, et al., (2002) Angew. Chem. Int. Ed. 41:2596-2599. By introducing an azide moiety into a protein structure, for example, one is able to incorporate a functional group that is chemically inert to amines, sulfhydryls, carboxylic acids, hydroxyl groups found in proteins, but that also reacts smoothly and efficiently with an acetylene moiety to form a cycloaddition product. Importantly, in the absence of the acetylene moiety, the azide remains chemically inert and unreactive in the presence of other protein side chains and under physiological conditions.
The present invention addresses, among other things, problems associated with the activity and production of bG-CSF polypeptides, and also addresses the production of a bG-CSF polypeptide with improved biological or pharmacological properties and/or improved therapeutic half-life.